Friction stir spot welding device and friction stir spot welding method

ABSTRACT

A tool driving section of a friction stir spot welding device is configured to cause each of a pin member and a shoulder member to advance and retract, and is controlled by a tool driving control section. A press-fit reference point setting section sets a position where the pin member or the shoulder member contacts an object to be welded as a press-fit reference point, and the tool driving control section controls the position of the pin member with respect to the shoulder member on the basis of the press-fit reference point, thereby controlling the press-fit depth of a rotating tool press-fitted from the surface of the object to be welded. This achieves the excellent welding quality at suitable precision according to welding conditions especially in a double-acting friction stir spot welding method.

TECHNICAL FIELD

The present invention relates to a friction stir spot welding device anda friction stir spot welding method, and in particular, to a frictionstir spot welding device and a friction stir spot welding method thatcan preferably control advancement and retraction of a rotating tool forfriction stir spot welding.

BACKGROUND ART

In transport means such as automobiles, railroad vehicles and airplanes,resistance spot welding or rivet connection has been employed to couplemetal materials to each other. However, in recent years, attention hasbeen given to friction stir spot welding as disclosed in Patent Document1 or 2. According to friction stir spot welding, the metal materials arewelded to each other by friction heat with a cylindrical rotating tool(welding tool) having a pin member at its front end. The rotating toolis configured to advanceable and retractable with respect to an objectto be welded, and advances at a pressure or speed in a predeterminedrange while rotating at high speed to be pushed into (press-fitted into)the object to be welded (metal materials). The metal materials aresoftened at a site where the rotating tool is press-fitted, and thesoftened metal materials are stirred to weld the object to be welded.

The friction stir spot welding disclosed in Patent Document 1 uses onlythe pin member as the rotating tool and thus, for convenience ofdescription, will be referred to as single-acting friction stir spotwelding. On the other hand, the friction stir spot welding disclosed inPatent Document 2 uses a substantially cylindrical pin member and asubstantially tubular shoulder member having a hollow for inserting thepin member thereinto as the rotating tool, and the pin member and theshoulder member can independently rotate, and advance and retract. Forconvenience of description, the friction stir spot welding of suchconfiguration will be referred to as double-acting friction stir spotwelding (refill friction spot joining). According to the double-actingfriction stir spot welding, by adjusting timings of advancement andretraction of the pin member and the shoulder member, a recess formed bypress-fitting of the pin member can be backfilled.

PRIOR ART DOCUMENTS Patent Documents

-   Patent Document 1: Patent Publication No. 4252403-   Patent Document 2: Japanese Patent Laid-Open Publication No.    2007-30017

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

According to the double-acting friction stir spot welding, the rotatingtool consists of a plurality of members: the pin member and the shouldermember. Thus, as compared to the single-acting friction stir spotwelding, the double-acting friction stir spot welding has moreconsiderations at execution, and it is more difficult to select mattersto be controlled at execution and moreover, if the selection ispossible, it is more difficult to specifically determine the matters tobe controlled. For this reason, a method of controlling thesingle-acting friction stir spot welding as disclosed in Patent Document1 cannot be applied as-is to the double-acting friction stir spotwelding.

Patent Document 2 describes the double-acting friction stir spot weldingcapable of preventing or effectively suppressing irregular burrs, butdoes not disclose the above-mentioned control that can achieve excellentwelding quality satisfying welding conditions with high precision.

The present invention is made to solve such problem, and its object isto provide a control technique capable of achieving the excellentwelding quality at suitable precision according to welding conditionsespecially in the double-acting friction stir spot welding method.

Solutions to the Problems

To solve the above-mentioned problem, a friction stir spot weldingdevice according to the present invention is a friction stir spotwelding device that welds an object to be welded by partial stirring ofa rotating tool, the device including: a cylindrical pin member as therotating tool, the pin member configured to rotate about an axis and beadvanceable and retractable in the axial direction; a tubular shouldermember configured to surround the pin member, rotate coaxially with thepin member, and be advanceable and retractable in the axial direction; atool driving section configured to cause each of the pin member and theshoulder member to advance and retract along the axis; a press-fitreference point setting section configured to set a position where theshoulder member or the pin member contacts the object to be welded, as apress-fit reference point; and a tool driving control section configuredto control the action of the tool driving section, wherein the tooldriving control section controls a relative position of the pin memberwith respect to the shoulder member or a relative position of theshoulder member with respect to the pin member on the basis of thepress-fit reference point set by the press-fit reference point settingsection, thereby controlling a press-fit depth of the pin member or theshoulder member press-fitted from a surface of the object to be welded.

The friction stir spot welding device may further include a displacementcalculating section configured to calculate quantity of displacement asdisplacement of a front end of the pin member or the shoulder member,wherein the tool driving control section may be configured to correctthe press-fit depth with the quantity of displacement.

The friction stir spot welding device may further include a clamp memberlocated outside the shoulder member, the clamp member being configuredto press the object to be welded from the surface; a clampposition-rotating tool position detecting section configured to detectthe position of a front end of the clamp member; and a clamp-tooldistance calculating section configured to calculate a distance betweenthe front end of the clamp member, which is detected by the clampposition-rotating tool position detecting section, and the front end ofthe pin member or the shoulder member, and the tool driving controlsection may be configured to adjust the press-fit depth on the basis ofthe distance calculated by the clamp-tool distance calculating section.

The friction stir spot welding device may further include a memorysection, and the memory section may be configured to store pressurizingforce adjusting data for adjusting pressurizing force of the rotatingtool press-fitted into the object to be welded, and the tool drivingcontrol section may be configured to read the pressurizing forceadjusting data from the memory section to control the pressurizingforce.

In the friction stir spot welding device, the pressurizing forceadjusting data as a value of a current applied to a motor of the tooldriving section may be stored in the memory section, and the tooldriving control section may be configured to adjust the current value tocontrol the pressurizing force.

In the friction stir spot welding device, the memory section mayindividually store the pressurizing force adjusting data in each of apress-fit action of press-fitting the pin member into the object to bewelded, a pull-out action of pulling the pin member out of the object tobe welded, and stopped state of the pin member, and the tool drivingcontrol section may be configured to determine whether the action of thepin member is the press-fit action, the pull-out action, or the stoppedstate, and read the pressurizing force adjusting data corresponding tothe determined action from the memory section to control the tooldriving section.

To solve the above-mentioned problem, a friction stir spot weldingmethod according to the present invention is a friction stir spotwelding method using a cylindrical pin member configured to rotate aboutan axis and be advanceable and retractable in the axial direction, and atubular shoulder member configured to surround the pin member, rotatecoaxially with the pin member, and be advanceable and retractable in theaxial direction, in a state where the pin member and the shoulder memberare advanceable and retractable, to weld an object to be welded having afront surface facing the pin member and the shoulder member by partialstirring, wherein a position where the pin member or the shoulder membercontacts the object to be welded is set as a press-fit reference point,and a relative position of the pin member with respect to the shouldermember or a relative position of the shoulder member with respect to thepin member is controlled on the basis of the press-fit reference point,thereby controlling a press-fit depth of the pin member or the shouldermember press-fitted from a surface of the object to be welded.

According to the friction stir spot welding method, quantity ofdisplacement as displacement of a front end of the pin member or theshoulder member may be calculated, and the press-fit depth may becorrected with the quantity of displacement.

According to the friction stir spot welding method, the surface of theobject to be welded may be pressed by a clamp member located outside theshoulder member, and a distance between a front end of the clamp memberand a front end of the pin member or the shoulder member may becalculated, and the press-fit depth may be adjusted on the basis of thedistance.

According to the friction stir spot welding method, pressurizing forceadjusting data for adjusting pressurizing force of the pin memberpress-fitted into the object to be welded may be stored in a memorysection, and the pressurizing force adjusting data may be read from thememory section to control the pressurizing force.

The above-mentioned and other objects, features, and advantages of thepresent invention will be apparent from following detailed descriptionof preferred Embodiments with reference to appended figures.

Effects of the Invention

As described above, according to the present invention, especially inthe double-acting friction stir spot welding, a control techniquecapable of achieving excellent welding quality with suitable precisionaccording to welding conditions can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic side view showing an example of configuration of afriction stir spot welding device in accordance with Embodiment 1 of thepresent invention.

FIG. 2A to FIG. 2F are process charts schematically showing an exampleof each stage of friction stir spot welding by the friction stir spotwelding device in FIG. 1.

FIG. 3A to FIG. 3F are process charts schematically showing anotherexample of each stage of friction stir spot welding by the friction stirspot welding device in FIG. 1.

FIG. 4 is a block diagram showing functional configuration of thefriction stir spot welding device shown in FIG. 1.

FIG. 5 is a flow chart showing an example of control of friction stirspot welding in the friction stir spot welding device in FIG. 4.

FIG. 6A and FIG. 6B are schematic views for describing setting of apress-fit reference point in the friction stir spot welding device inFIG. 1.

FIG. 7 is a block diagram showing functional configuration of a frictionstir spot welding device in accordance with Embodiment 2 of the presentinvention.

FIG. 8 is a block diagram showing functional configuration of a frictionstir spot welding device in accordance with Embodiment 3 of the presentinvention.

FIG. 9 is a block diagram showing functional configuration of a frictionstir spot welding device in accordance with Embodiment 4 of the presentinvention.

EMBODIMENTS OF THE INVENTION

Preferred Embodiments of the present invention will be described belowwith reference to figures. Throughout the figures, the same orequivalent elements are given the same reference signs and overlappingdescription thereof is omitted.

Embodiment 1 [Friction Stir Spot Welding Device]

A basic configuration of a friction stir spot welding device inaccordance with Embodiment 1 of the present invention will be describedwith reference to FIG. 1.

As shown in FIG. 1, a friction stir spot welding device 50A inaccordance with this embodiment includes a rotating tool 51, a toolfixing section 52, a tool driving section 53, a clamp member 54, alining support section 55, and a lining member 56.

The rotating tool 51 is supported by the tool fixing section 52, anddriven to advance and retract and rotate by the tool driving section 53.The rotating tool 51, the tool fixing section 52, the tool drivingsection 53, and the clamp member 54 are provided above the liningsupport section 55 constituted as a C-gun (C-type frame), and the liningmember 56 is provided below the lining support section 55. Accordingly,the rotating tool 51 and the lining member 56 are attached to the liningsupport section 55 as opposed to each other, and an object to be welded60 is arranged between the lining member 56 and the rotating tool 51.

The rotating tool 51 consists of a pin member 11 and a shoulder member12. The tool fixing section 52 consists of a rotating tool fixingsection 521 and a clamp fixing section 522, and the tool driving section53 consists of a pin driving section 531, a shoulder driving section532, a rotational driving section 533, and a clamp driving section 41.The clamp member 54 is fixed to the clamp fixing section 522 via theclamp driving section 41. The clamp driving section 41 is formed of aspring.

The pin member 11 is substantially tubular or cylindrical, and althoughnot shown in detail, is supported by the rotating tool fixing section521. The pin member 11 is rotated about an axis Xr (a rotary axisrepresented by a dot-and-dash line in the figure) by the rotationaldriving section 533, and can be advanced and retracted along a dashedarrow 11 or the axis Xr (in the vertical direction in FIG. 1) by the pindriving section 531. The shoulder member 12 is shaped substantially likea hollow tube, and the pin member 11 is inserted into the hollow tube,so that the rotating tool fixing section 521 supports the shouldermember 12 outside the pin member 11 so as to surround the pin member 11.The shoulder member 12 is rotated about the same axis Xr as the rotaryaxis of the pin member 11 by the rotational driving section 533, and canbe advanced and retracted along a dashed arrow P2 or the axis Xr by theshoulder driving section 532.

In this manner, both of the pin member 11 and the shoulder member 12 aresupported by the rotating tool fixing section 521 in this embodiment,and are integrally rotated about the axis Xr by the rotational drivingsection 533. Further, the pin member 11 and the shoulder member 12 eachcan be advanced and retracted along the axis Xr by the pin drivingsection 531 and the shoulder driving section 532. With the configurationshown in FIG. 1, the pin member 11 can advance and retract alone andwith advancement and retraction of the shoulder member 12; however, thepin member 11 and the shoulder member 12 can independently advance andretract.

The clamp member 54 is provided outside the shoulder member 12, and likethe shoulder member 12, is shaped substantially like a hollow tube, andthe shoulder member 12 is inserted into the hollow. Accordingly, thesubstantially tubular shoulder member 12 is located on the periphery ofthe pin member 11, and the substantially tubular clamp member 54 islocated on the periphery of the shoulder member 12. In other words, theclamp member 54, the shoulder member 12, and the pin member 11 arecoaxially nested.

The clamp member 54 presses the object to be welded 60 from one surface(front surface), and in this embodiment, is supported by the clampfixing section 522 via the clamp driving section 41. Accordingly, theclamp member 54 is biased toward the lining member 56. The clamp fixingsection 522 supports the rotating tool fixing section 521 via therotational driving section 533. The clamp fixing section 522 can beadvanced and retracted along a dashed arrow P3 (having the samedirections as those of the dashed arrows P1 and P2) by the shoulderdriving section 532. The clamp driving section 41 is not limited to thespring, and may be any means for biasing or pressurizing force the clampmember 54, for example, a mechanism using gas pressure, hydraulicpressure, or servo motor. The clamp driving section 41 may be advancedand retracted by the shoulder driving section 532 as shown in FIG. 1, ormay be independently advanced and retracted irrespective of the shoulderdriving section 532.

As described above, the rotating tool 51, the tool fixing section 52,the tool driving section 53, and the clamp member 54 are provided on thelining support section 55 as opposed to the lining member 56. The pinmember 11 and the shoulder member 12, which constitute the rotating tool51, and the clamp member 54 include a contact surface 11 a, a contactsurface 12 a, and a contact surface 54 a, respectively, and thesecontact surfaces 11 a, 12 a, 54 a can be advanced and retracted by thetool driving section 53, and contact a front surface (first surface, onesurface) of the object to be welded 60 arranged between the contactsurfaces and the lining member 56. The lining member 56 is opposed tothe pin member 11 and the shoulder member 12, and the clamp member 54,and contacts a back surface of the object to be welded 60. In FIG. 1,the lining member 56 has a flat surface that conforms to the backsurface of the flat plate-like object to be welded 60.

The lining member 56 is located on the side, toward which the pin member11 and the shoulder member 12 advance, and a support surface 56 a of thelining member 56 supports the back surface of the object to be welded 60in the state where the front surface of the object to be welded 60 facesthe pin member 11 and the shoulder member 12. The lining member 56 maybe configured in any manner as long as it can properly support theobject to be welded 60 for friction stir spot welding. The lining member56 is generally a flat plate having the support surface 56 a that canstably support the plate-like object to be welded 60, but may have anyconfiguration other than the flat plate according to the shape of theobject to be welded 60. For example, the lining members 56 of pluraldifferent shapes may be prepared separately, and the lining member 56may be removable from the lining support section 55 to be replaced withone of the prepared lining members 56 according to the type of theobject to be welded 60.

Specific configurations of the rotating tool 51, the tool fixing section52, and the tool driving section 53 in this embodiment are not limitedto the above-mentioned configurations, and may be any configuration wellknown in the field of friction stir spot welding. For example, the pindriving section 531, the shoulder driving section 532, and therotational driving section 533, which constitute the tool drivingsection 53 in this embodiment, each are formed of a motor and gearmechanism well known in the field of friction stir spot welding. In thefriction stir spot welding device 50A, the clamp member 54 may beomitted, or may be removable from the lining support section 55 asneeded. Other members not shown in FIG. 1 may be included.

The lining support section 55 is formed of a C-gun in this embodiment,but is not limited to this as long as it can support the pin member 11and the shoulder member 12 so as to allow them to advance and retract,as well as support the lining member 56 at a position opposed to therotating tool 51.

In this embodiment, the lining support section 55 is attached to a frontend of an arm not shown. The arm is included in a friction stir spotwelding robot not shown in FIG. 1. Thus, the lining support section 55can be deemed to be included in the friction stir spot welding robot.The configuration of the friction stir spot welding robot, including thelining support section 55 and the arm, is not specifically limited, andany configuration well known in the field of the friction stir spotwelding, such as a multiple joint robot, can be preferably used.

The friction stir spot welding device 50A including the lining supportsection 55 is not applied only to the friction stir spot welding robot.For example, the friction stir spot welding device 50A can be preferablyapplied to well-known processing machines such as NC machine tools,large C frames, and auto-riveters. Two pairs or more of robots may beused such that the friction stir spot welding device confronts thelining member 56. Providing that the object to be welded 60 can bestably subjected to friction stir spot welding, a friction stir spotwelding device can be applied as a handheld configuration in contrastwith the stationary friction stir spot welding device 50A in thisembodiment, or a robot can be used as a positioner for the object to bewelded 60.

[Friction Stir Spot Welding Method]

Next, a specific process of a friction stir spot welding method usingthe above-mentioned friction stir spot welding device 50A will bedescribed with reference to FIG. 2A to FIG. 2F and FIG. 3A to FIG. 3F.In FIG. 2A to FIG. 2F and FIG. 3A to FIG. 3F, two metal plates 61, 62are used as the object to be welded 60, and these metal plates 61, 62are stacked and coupled to each other by spot welding.

In FIG. 2A to FIG. 2F and FIG. 3A to FIG. 3F, an arrow p represents adirection in which the rotating tool 51 is moved (corresponding to thedirection represented by the dashed arrow P1 to P2 in FIG. 1), an arrowr represents a direction in which the rotational members (the pin member11 and the shoulder member 12) are rotated, and a block arrow Frepresents a direction in which a force is exerted on the metal plates61, 62. In FIG. 2A to FIG. 2F and FIG. 3A to FIG. 3F, for clearlydescribing the position of the constituents in each step and the weldingsite of the metal plates 61, 62, as to the arrow p and the block arrowF, the reference numerals “p” and “F” are expressed in only FIG. 2A, andas to the arrow r, the reference numeral “r” is expressed in only FIG.2B. Although a force is exerted also from the lining member 56 to themetal plates 61, 62, for convenience of description, the force is notshown in FIG. 2A to FIG. 2F. Further, to distinguish the shoulder member12 from the pin member 11 and the clamp member 54, the shoulder member12 is halftone-hatched.

First, a series of steps in FIG. 2A to FIG. 2F will be described. In theseries of steps, the pin member 11 is press-fitted into the metal plates61, 62 before the shoulder member 12 is.

Specifically, as shown in FIG. 2A, the rotating tool 51 is made close tothe metal plates 61, 62 (the arrow p in this figure) to bring thecontact surface 54 a (not shown in FIG. 2A to FIG. 2F) of the clampmember 54 into contact with a front surface 60 e of the upper metalplate 61, and to bring the lining member 56 into contact with a backsurface 60 d of the lower metal plate 62. As a result, the clamp member54 and the lining member 56 sandwich the metal plates 61, 62therebetween, and pressure from the clamp member 54 (the block arrow Fin this figure) generates a clamping force.

Next, as shown in FIG. 2B, the rotational members of the rotating tool51 come close to the metal plates 61, 62, bringing the contact surface11 a (not shown in FIG. 2A to FIG. 2F) of the pin member 11 and thecontact surface 12 a (not shown in FIG. 2A to FIG. 2F) of the shouldermember 12 into contact with the front surface 60 c of the metal plate61. In this state, contraction of the clamp driving section 41 formed ofthe spring generates the clamping force of the clamp member 54. Then,the pin member 11 and the shoulder member 12 are brought into contactwith the front surface 60 c of the metal plate 61, and are rotated(about the arrow r in this figure).

In this state, since both of the pin member 11 and the shoulder member12 do not advance nor retract, the front surface 60 c of the metal plate61 is “preheated”. Thereby, the metal material in a contact area of themetal plate 61 is softened by heat generated by friction, forming aplastic flowing portion 60 a near the front surface 60 c of the metalplate 61.

Next, as shown in FIG. 2C, the pin member 11 is projected from theshoulder member 12 by the pin driving section 531 not shown, therebyfurther advancing (pressing) the pin member 11 inwards from the frontsurface 60 c of the metal plate 61. At this time, the softened region ofthe metal material ranges from the upper metal plate 61 to the lowermetal plate 62 to increase the plastic flowing portion 60 a. Since thesoftened metal material of the plastic flowing portion 60 a is furtherpushed aside by the pin member 11 and flows from immediately below thepin member 11 to immediately below the shoulder member 12, the shouldermember 12 retracts and floats upward when viewed from the pin member 11.

Next, as needed, as shown in FIG. 2D, a step where the pin member 11protruded by the pin driving section 531 not shown is graduallyretracted (drawn), and with the retraction of the pin member 11, theshoulder member 12 is advanced into (press-fitted into) the metal plate61 may be performed. In a below-mentioned step in FIG. 2E, the frontsurface 60 c of the metal plate 61 is shaped. However, if the frontsurface 60 c is not sufficiently shaped at this time, the step shown inFIG. 2D may be performed.

After that, after the step in FIG. 2C, the pin member 11 is graduallyretracted, and after the step in FIG. 2D, the shoulder member 12 isgradually retracted. At this time, as represented by the block arrows inFIG. 2C and FIG. 2D, even during retraction of the pin member 11 or theshoulder member 12, the pressurizing force from its front end ismaintained. In the former case, since rotation and pressure of theshoulder member 12 is maintained while the pin member 11 is retracted,the softened metal material of the plastic flowing portion 60 a flowsfrom immediately below the shoulder member 12 to immediately below thepin member 11, backfilling the recess. In the latter case, sincerotation and pressure by the pin member 11 is maintained while theshoulder member 12 is retracted, the recess caused by press-fit of theshoulder member 12 is backfilled.

After that, as shown in FIG. 2E, the contact surface 11 a of the pinmember 11 is aligned with (flush with) the contact surface 12 a of theshoulder member 12 without any substantial step therebetween. Thereby,the front surface 60 c of the metal plate 61 is shaped to achieve analmost flat surface without any substantial recess.

Finally, as shown in FIG. 2F, the rotating tool 51 and the lining member56 are separated from the metal plates 61, 62 to finish the series offriction stir spot welding. At this time, rotation (and pressure) causedby contact with the rotating tool 51 is no longer transmitted to themetal plates 61, 62. Thus, plastic flow of the plastic flowing portion60 a extending on both the metal plates 61, 62 is stopped, and becomes awelded portion 60 b. As a result, the two metal plates 61, 62 arecoupled to each other with the welded portion 60 b.

Next, a series of steps in FIG. 3A to FIG. 3F will be described. In theseries of steps, the shoulder member 12 is press-fitted into the metalplates 61, 62 before the pin member 11 is. In FIG. 3A to FIG. 3F, thelining member 56 also exerts a force to the metal plates 61, 62, but forconvenience of description, the force is not shown.

Since steps in FIG. 3A and FIG. 3B are the same as the steps in FIG. 2Aand FIG. 2B, description thereof is omitted. Next, as shown in FIG. 3C,by protruding the shoulder member 12 further from the pin member 11 bythe shoulder driving section 532 not shown, the shoulder member 12 isfurther advanced inwards (press-fitted into) from the front surface 60 cof the metal plate 61. Thus, the plastic flowing portion 60 a rangesfrom the upper metal plate 61 to the lower metal plate 62, the softenedmetal material of the plastic flowing portion 60 a is pushed aside bythe shoulder member 12 to flow from immediately below the shouldermember 12 to immediately below the pin member 11, resulting in that thepin member 11 retracts and floats upward when viewed from the shouldermember 12.

Next, as needed, as shown in FIG. 3D, a step where the protrudingshoulder member 12 is gradually retracted (drawn), and with theretraction, the pin member 11 is advanced (press-fitted) into the metalplate 61 may be performed. Then, after the step in FIG. 3C, the shouldermember 12 is gradually retracted, and after the step in FIG. 3D, the pinmember 11 is gradually retracted. This backfills the recess generated bypress-fit of the shoulder member 12 or the pin member 11.

After that, as shown in FIG. 3E, the contact surface 11 a of the pinmember 11 is aligned with (flush with) the contact surface 12 a of theshoulder member 12 without any substantial step therebetween. Finally,as shown in FIG. 3F, the rotating tool 51 and the lining member 56 areseparated from the metal plates 61, 62 to finish the series of frictionstir spot welding.

In this embodiment, the stage shown in FIG. 2A or FIG. 3A is referred toas a “preparation stage” of friction stir spot welding, the stage inFIG. 2B or FIG. 3B is referred to as a “pre-heating stage”. In the stageshown in FIG. 2C to FIG. 2E or FIG. 3C to FIG. 3E, a press-fit depth(press-fit/pull-out depth or advance/retract depth) of the pin member 11or the shoulder member 12 is controlled by controlling the relativeposition of the pin member 11 with respect to the shoulder member 12 (orthe relative position of the shoulder member 12 with respect to the pinmember 11). Accordingly, these stages are referred to as a “tool controlstage”. The stage shown in FIG. 2F or FIG. 3F is referred to as a“completion stage” of friction stir spot welding.

In this embodiment, as the “tool control stage”, three stages in total:a stage in FIG. 2C or FIG. 3C, a stage in FIG. 2D or FIG. 3D, and astage in FIG. 2E or FIG. 3E are executed. For convenience ofdescription, each of these stages is given a specific stage name.Specifically, the stage in FIG. 2C or FIG. 3C is referred to as a“press-fit stage”, the stage in FIG. 2D or FIG. 3D is referred to as a“backfill stage”, and the stage in FIG. 2E or FIG. 3E is referred to asa “shaping stage”.

In this embodiment, the press-fit stage, the backfill stage, and theshaping stage are illustrated as the tool control stage and however, asdescribed above, the tool control stage may be at least the press-fitstage and the shaping stage. The backfill stage is the tool controlstage performed as needed and thus, may be omitted. A tool control stageincluding four or more stages is possible.

As described above, the friction stir spot welding device 50A includesthe pin member 11 and the shoulder member 12 as the rotating tool 51,and the rotating tool 51 partially stirs the object to be welded 60 (themetal plates 61, 62 in this example) to weld the object to be welded 60.Since the two members of the rotating tool 51 can consecutively performthe stages shown in FIG. 2A to FIG. 2F or FIG. 3A to FIG. 3F, ascompared to single-acting friction stir spot welding, irregularity inthe front surface 60 c of the object to be welded 60 can be reduced asmuch as possible by backfilling of the recess.

[Control Configuration of Friction Stir Spot Welding Device]

Next, control configuration of the friction stir spot welding device50A, which serves to perform the series of stages in friction stir spotwelding, will be specifically described with reference to FIG. 4.

As shown in FIG. 4, the friction stir spot welding device 50A furtherincludes a tool driving control section 21, a press-fit reference pointsetting section 22, a memory section 31, an input section 32, and apressurizing force detecting section 33.

The tool driving control section 21 controls the tool driving section53. That is, the tool driving control section 21 controls the pindriving section 531, the shoulder driving section 532, and therotational driving section 533, which constitute the tool drivingsection 53, to control switching between advancement or retraction ofthe pin member 11 and the shoulder member 12, and the position of thefront ends, moving speed, and moving direction of the pin member 11 andthe shoulder member 12 during advancement or retraction. In thisembodiment, the tool driving control section 21 controls the tooldriving section 53 on the basis of the reference point set by thepress-fit reference point setting section 22, thereby controlling therelative position of the front end of the pin member 11 with respect tothe front end of the shoulder member 12.

The press-fit reference point setting section 22 serves to set theposition where the pin member 11 or the shoulder member 12 contacts theobject to be welded 60, as the press-fit (pushing) reference point ofthe pin member 11 or the shoulder member 12. The pin member 11 or theshoulder member 12 stays on the front surface 60 c of the object to bewelded 60 for a short but certain period until the material becomessoftened. Then, for the shoulder member 12, the press-fit referencepoint setting section 22 derives the position where the shoulder member12 contacts the object to be welded 60 and stays there for a certainperiod from positional information of the shoulder member 12 (such asthe moving speed obtained by an encoder), which is obtained from thetool driving control section 21, and sets the derived position as apress-fit reference point. The press-fit reference point becomes areference point for the press-fit depth at press-fit of the pin member11 and the shoulder member 12 into the object to be welded 60. Thepress-fit reference point for the pin member 11 is set in the samemanner.

As a matter of course, the press-fit reference point setting section 22may set the position offset from the front surface 56 a of the liningmember 56 by a nominal or pre-measured thickness of the object to bewelded 60, as the press-fit reference point, and in this case,operations of measuring and inputting the thickness are required. Whenthe position offset from the front surface 56 a of the lining member 56by the nominal or pre-measured thickness of the object to be welded 60is set as the press-fit reference point, since the pin member 11 or theshoulder member 12 contacts the material with considerable pressurizingforce, it is necessary to consider deformation of the friction stir spotwelding device 50A due to the pressurizing force. Further, deviation inlength, which is caused by thermal expansion of the pin member 11 andthe shoulder member 12 during preheating, can occur as an error. Whenthe position where the shoulder member 12 (rotating tool 51) contactsthe object to be welded 60 and stays there for a certain period is setas the press-fit reference point, deformation of the friction stir spotwelding device 50A, deformation of the object to be welded 60, anddeviation in length due to thermal expansion of the pin member 11 andthe shoulder member 12 can be eliminated.

Configuration of the tool driving control section 21 and the press-fitreference point setting section 22 is not specifically limited and inthis embodiment, the tool driving control section 21 is formed of theCPU in the microcomputer, and makes calculation on the action of thetool driving section 53, and the press-fit reference point settingsection 22 is configured as a function of the tool driving controlsection 21. That is, the CPU as the tool driving control section 21 mayoperate according to a program stored in the memory section 31 oranother memory section to realize the press-fit reference point settingsection 22.

As long as the press-fit reference point setting section 22 can set thepress-fit reference point on the basis of the motor rotationalinformation (for example, motor rotational angle or rotational speed)generated by the tool driving control section 21, it is not necessarilya function of the tool driving control section 21. For example, thepress-fit reference point setting section 22 may be configured as awell-known logical circuit or like including a switching element, asubtractor, or a comparator, etc.

The memory section 31 readably stores various types of data, and in thisembodiment, as shown in FIG. 4, stores pressurizing force/motor currentdatabases Db1 to Db3. The tool driving control section 21 uses thepressurizing force/motor current databases Db1 to Db3 to control thetool driving section 53.

The memory section 31 is formed of a storage device such as a well-knownmemory, a hard disc, or the like. The memory section 31 is notnecessarily a single unit, and may be formed of a plurality of storagedevices (for example, a random access memory and a hard disc drive).When the tool driving control section 21 is a microcomputer, at least apart of the memory section 31 may be configured as an internal memory inthe microcomputer, or as an independent memory. The memory section 31may store data other than the databases, and read the data from anysection other than the tool driving control section 21. As a matter ofcourse, data may be written from the tool driving control section 21 orso on.

The input section 32 enables inputting of various parameters on thecontrol of friction stir spot welding and other data into the tooldriving control section 21, and is formed of a well-known input devicesuch as a keyboard, a touch panel, or a button switch. In thisembodiment, at least welding conditions for the object to be welded 60,for example, data on the thickness and the material of the object to bewelded 60 can be inputted by the input section 32.

When the rotating tool 51 (the pin member 11, the shoulder member 12, orthe both) contacts or is press-fitted into the object to be welded 60,the pressurizing force detecting section 33 detects the pressurizingforce exerted on the object to be welded 60 from the rotating tool 51.In this embodiment, a load cell is used as the pressurizing forcedetecting section 33. However, the pressurizing force detecting section33 is not limited to the load cell, and may be any well-knownpressurizing force detector.

It is noted that, in the friction stir spot welding device 50A inaccordance with Embodiment 1, the pressurizing force detecting section33 is not essential constitute, but used to acquire the pressurizingforce/motor current databases Db1 to Db3 stored in the memory section31, and can be used as redundant information of the press-fit referencepoint setting section 22, enhancing convenience in controlling drivingof the rotating tool 51. The tool driving control section 21 may be usedfor feedback control from the pressurizing force detecting section 33 inplace of the pressurizing force/motor current databases Db1 to Db3.

[Control by Tool Driving Control Section]

Next, control of the tool driving section 53 by the tool driving controlsection 21, in particular, control of the relative position of the frontend of the pin member 11 with respect the front end of to the shouldermember 12 on the basis of the press-fit reference point, and control ofthe press-fit depth of the rotating tool 51 will be describedspecifically with reference to FIG. 5, FIG. 6A and FIG. 6B.

First as shown in FIG. 5, the tool driving control section 21 controlsthe tool driving section 53 to cause the rotating tool 51 to move towardthe front surface 60 c of the object to be welded 60 supported by thelining member 56 (Step S101). Since this stage corresponds to thepreparation stage (refer to FIG. 2A or FIG. 3A), the clamp member 54contacts the front surface 60 c, while the pin member 11 and theshoulder member 12 are located at a default position and does notcontact the front surface 60 c.

Next, the tool driving control section 21 brings the shoulder member 12of the rotating tool 51 into contact with the front surface 60 c of theobject to be welded 60, and starts to press (push) the object to bewelded 60 (Step S102). At this time, although the shoulder member 12contacts the front surface 60 c while rotating, the shoulder member 12may contact the front surface 60 c without rotating and then, start torotate. Then, the tool driving control section 21 sets the positionwhere the shoulder member 12 contacts the front surface 60 c of theobject to be welded 60, as the press-fit reference point (Step S103).

Specifically, for example, as shown in FIG. 6A, the object to be welded60 is supported by the lining member 56, the front end of the pin member11 is aligned with the front end of the shoulder member 12, and thefront surface 60 c of the object to be welded 60 and the front ends ofthe pin member 11 and the shoulder member 12 have a spacing Detherebetween. Here, given that the distance between the front end of therotating tool 51 (the pin member 11 and the shoulder member 12) and thesupport surface 56 a of the lining member 56 is a “tool distance”, inthe state shown in FIG. 6A, a tool distance Dt0 includes the spacing De.

Given that it is attempted to press-fit the pin member 11 or theshoulder member 12 to a press-fit depth d0. At this time, the spacing Dedoes not contribute to control of the press-fit depth d0. Thus, as shownin FIG. 6B, when the shoulder member 12 (and the pin member 11) isadvanced, contacts the front surface 60 c of the object to be welded 60and stays there for a certain period, in FIG. 6B, the press-fitreference point setting section 22 sets a position of a tool distanceDt1 as the press-fit reference point. That is, the press-fit referencepoint setting section 22 corrects the position where the shoulder member12 contacts and stays to a point of press-fit depth=0 (0 point), andusing the 0 point as a reference, the tool driving control section 21controls advancement or retraction of the pin member 11 (or the shouldermember 12 or the both).

Next, the tool driving control section 21 instructs movement of the pinmember 11 from a default position to an inputted position (designatedposition) in a preheating stage (refer to FIG. 2B or FIG. 3B), andincreases the pressurizing force of the shoulder member 12 to apredetermined value (Step S104). By continuing to rotate the pin member11 and the shoulder member 12 in this state, the welded portion of theobject to be welded 60 is preheated.

The default position, the inputted position, and the pressurizing forceare parameters set for preheating, and suitable values are appropriatelyset depending on the specific configuration of the friction stir spotwelding device 50A, and material, thickness, and shape, etc. of theobject to be welded 60. Each parameter including the inputted positionin each of below-mentioned stages is inputted to the tool drivingcontrol section 21 by the input section 32, and is stored in the memorysection 31. According to the control stage, the tool driving controlsection reads the parameters from the memory section 31, and uses theread parameters for control.

Next, control by the tool driving control section 21 shifts to the toolcontrol stage. In this embodiment, the tool control stage consists of apress-fit stage, a backfill stage, and a shaping stage (refer to FIG. 2Cto FIG. 2E and FIG. 3C to FIG. 3E) and thus, the control will bedescribed below using these three stages as an example. In the followingdescription on the control, for convenience, the example shown in FIG.2C to FIG. 2E, that is, the case where the pin member 11 is firstpress-fitted is used as an example.

First, the tool driving control section 21 moves the shoulder member 12to a inputted position in the press-fit stage (refer to FIG. 2C), andalso moves the pin member 11 to a inputted position in the press-fitstage (Step S105). Here, advancement and retraction of the shouldermember 12 and the pin member 11 to the respective inputted positions iscontrolled according to a value of a current applied to a motor of thetool driving section 53 (motor current value). For the shoulder member12, when the shoulder member 12 is controlled according to the motorcurrent value and reaches the inputted position, advancement orretraction is finished. The inputted positions of the pin member 11 orthe shoulder member 12 in the press-fit stage are set to the positionwhere the pin member 11 or the shoulder member 12 is pushed into(press-fitted into) the object to be welded 60, while the inputtedposition of the shoulder member 12 is set to a position where theshoulder member 12 is not pushed into the object to be welded 60 andpresses the front surface 60 c in the pressing state.

Next, in the backfill stage, the tool driving control section 21 movesthe shoulder member 12 from the inputted position in the press-fit stageto a inputted position in the backfill stage (refer to FIG. 2D), andalso moves the pin member 11 from the inputted position in the press-fitstage to the inputted position in the backfill stage (Step S106). Asdescribed above, providing that the front surface 60 c of the object tobe welded 60 can be sufficiently shaped in the next shaping stage, thebackfill stage may be omitted.

Next, the tool driving control section 21 moves the shoulder member 12to a inputted position in the shaping stage (refer to FIG. 2E), and alsomoves the pin member 11 to an inputted position in the shaping stage(Step S107). The inputted positions of the pin member 11 and theshoulder member 12 in the shaping stage are set to be the almost sameposition as the front surface 60 c of the object to be welded 60(generally, the press-fit reference point).

In the three tool control stages, the position of the pin member 11 andthe shoulder member 12 is controlled by the tool driving control section21 using the press-fit reference point as a reference. Thus, sinceadvancement and retraction of the pin member 11 and the shoulder member12 subjected to “0-point correction” of press-fit by the press-fitreference point setting section 22 is controlled, the tool drivingcontrol section 21 can suitably control the relative position of the pinmember 11 with respect to the shoulder member 12, and can controlwithout considering the spacing De (refer to FIG. 6B) between the frontsurface 60 c of the object to be welded 60 and the rotating tool 51 (thepin member 11 and the shoulder member 12), the press-fit depth can becontrolled at higher precision.

After that, the tool driving control section 21 moves the pin member 11to a default position, and controls the tool driving section 53 torelease contact of the shoulder member 12 with the object to be welded60 (Step S108), to finish a series of process of friction stir spotwelding.

As shown in FIG. 6B, the tool distance Dt1 subjected to 0-pointcorrection by the press-fit reference point setting section 22corresponds to the thickness of the object to be welded 60. Accordingly,the friction stir spot welding device 50B in this embodiment can causethe shoulder member 12 to contact the object to be welded 60 for 0-pointcorrection, measuring the thickness of the object to be welded 60.

In Steps S105 to S107 surrounded with a broken line Ct in FIG. 5, thetool driving control section 21 can control the press-fit depth of thepin member 11 and the shoulder member 12, and as shown in FIG. 4, readbelow-mentioned pressurizing force adjusting data from the memorysection 31, and control the pressurizing force of the pin member 11 andthe shoulder member 12.

The pressurizing force adjusting data may be any data as long as it canbe used to control the tool driving section 53, and is preferably, datafor adjusting the pressurizing force in the state where the rotatingtool 51 is press-fitted into the object to be welded 60. In thisembodiment, it is the above-mentioned motor current value. The motorcurrent value is written in the form of database (or table) so as toaddress with change in the pressurizing force, and as described above,the pressurizing force/motor current databases Db1 to Db3 are stored inthe memory section 31. The tool driving control section 21 reads thecurrent value to adjust the motor current value, thereby controlling thepressurizing force of the pin member 11 and the shoulder member 12.

Especially in this embodiment, the number of the databases (or tables)for the motor current value, which are stored in the memory section 31,is three, not one. The pressurizing force/motor current database Db1contains the motor current values for advancing or retracting theshoulder member 12 when advancement and retraction of the pin member 11is stopped, the pressurizing force/motor current database Db2 containsthe motor current values for advancing or retracting the shoulder member12 when the pin member 11 is press-fitted into (pushed into) the objectto be welded 60, and the pressurizing force/motor current database Db3contains the motor current values for advancing or retracting theshoulder member 12 when the pin member 11 is pulled out of the object tobe welded 60.

The tool driving control section 21 determines whether the pin member 11is press-fitted, is pulled out, or is stopped without being press-fittedor pulled out, and reads the motor current value in the correspondingaction from the three pressurizing force/motor current databases Db1 toDb3 to control the tool driving section 53. In the state where theobject to be welded 60 is pressed, the pressurizing force changesaccording to the action of the pin member 11. Thus, by adjusting thepressurizing force according to the action of the pin member 11, thepressurizing force can be controlled more suitably.

Specifically, providing that the state where the pin member 11 isstopped (at stopping) is a reference state, in the state where the pinmember 11 is press-fitted (at press-fit action), the pressurizing forcebecomes relatively high, and in the state where the pin member 11 ispulled out (at pull-out action), the pressurizing force becomesrelatively low. Accordingly, at press-fit action, pull-out action, andstopping of the pin member 11, different motor current values arewritten in databases and stored in the memory section 31. The tooldriving control section 21 determines the type of the action of the pinmember 11, for example, on the basis of the moving speed and the movingdirection of the pin member 11, and reads the motor current valuecorresponding to the determined action to adjust the pressurizing force.

The motor current values stored in the pressurizing force/motor currentdatabases Db1 to Db3 are not specifically limited, and experimentallysuitable values may be derived according to the type of the motor of thetool driving section 53, the change amount in the pressurizing force,the type of a gear mechanism transmitting the rotation driving power, orso on, and be written in databases (or tables). Only two databases maybe stored, or four or more databases may be stored as needed.

In this embodiment, the moving speed and the moving direction of the pinmember 11 are used as indicators for determining the type of the actionof the pin member 11. However, the indicators are not limited to themoving speed and the moving direction, and may be any well-knownparameter as long as it can properly determine the press-fit action,pull-out action, and stopping action. When the moving speed of the pinmember 11 is used as the indicator, a speed deadband at switchingbetween the press-fit action and the pull-out action can be set.

Provided that the state where the pin member 11 moves at a speedexceeding 0.05 mm/s is determined as the press-fit action (+ direction)or the pull-out action (− direction) on the basis of the movingdirection, the range of −0.05 to +0.05 mm/s is set as the deadband. As aresult, since the boundary for determining the press-fit action or thepull-out action is no longer a pinpoint threshold, the possibility thatthe database to be read frequently changes with speed change, leading tounstable adjustment of the pressurizing force can be suppressed orprevented.

As described above, the friction stir spot welding device 50A in thisembodiment can suitably control the relative position of the pin member11 with respect to the shoulder member 12, and especially, the press-fitdepth of the pin member 11 and the shoulder member 12, or thepressurizing force of the pin member 11 onto the object to be welded 60.Therefore, excellent welding quality can be achieved at suitableprecision according to welding conditions.

Although in this embodiment the configuration for controlling thepress-fit depth and the pressurizing force has been described in detail,the configuration according to the present invention only needs tocontrol the relative position of the pin member 11 with respect to theshoulder member 12 on the basis of the press-fit reference point andthus, for example, may control the moving speed of the pin member 11 andthe shoulder member 12 in advancing and retracting directions.

Embodiment 2

Configuration of a friction stir spot welding device in accordance withEmbodiment 2 of the present invention will be specifically describedwith reference to FIG. 7. As shown in FIG. 7, a friction stir spotwelding device 50B in this embodiment is the same as the friction stirspot welding device 50A in Embodiment 1 in basic configuration, but isdifferent from the friction stir spot welding device 50A in that a toolposition acquiring section 23 and a displacement calculating section 24are provided, and a deformation/distortion database Db4 is stored in thememory section 31.

The tool position acquiring section 23 acquires a tool position from thepin driving section 531 and the shoulder driving section 532. The toolposition is a position of the front end of the pin member 11 or thefront end of the shoulder member 12, and the tool driving controlsection 21 generates the tool distance based on the tool position. Asdescribed in Embodiment 1 (refer to FIG. 6A and FIG. 6B), the tooldistance is defined as a distance between the front end of the pinmember 11 or the front end of the shoulder member 12, and the supportsurface 56 a.

The displacement calculating section 24 calculates various types ofdisplacement (quantity of displacement), which affects advancement orretraction of the rotating tool 51, from the pressurizing force detectedby the pressurizing force detecting section 33. Examples of the quantityof displacement includes quantity of displacement of the rotating tool,quantity of deformation of the lining support section 55, and quantityof distortion of the tool fixing section 52 and the tool driving section53. However, the quantity of displacement is not limited to these, andmay be backlash of the tool driving section 53. In this embodiment, thedisplacement calculating section 24 reads the quantity of displacementcorresponding to the pressurizing force from the deformation/distortiondatabase Db4 stored in the memory section 31.

In this embodiment, the pin driving section 531 and the shoulder drivingsection 532 each are formed of a well-known motor. The tool positionacquiring section 23 can acquire the tool position by use of an encoderor the like provided in the motor, and the displacement calculatingsection 24 can calculate tool quantity of displacement on the basis ofthe pressurizing force acquired by the pressurizing force detectingsection 33, and the deformation/distortion database Db4 recorded in thememory section 31. The tool driving control section 21 generates thetool distance based on the tool position, and corrects the tool distanceaccording to the tool quantity of displacement.

The quantity of displacement of the rotating tool is defined asdisplacement between the thickness of the object to be welded 60, whichis inputted as the welding condition, and the position of the contactsurface 12 a at the time when the pin member 11 or the shoulder member12 contacts the front surface 60 c of the object to be welded 60, in thestate where the support surface 56 a of the lining member 56 supportsthe object to be welded 60 (the stacked metal plates 61, 62). Theposition of the front end of the pin member 11 or the shoulder member 12at the time when the pin member 11 or the shoulder member 12 contactsthe front surface of the object to be welded 60 can be acquired by usingthe above-mentioned encoder (the shoulder driving section 532).Occurrence of the quantity of displacement of the rotating tool affectscontrol of the position of the front end of the pin member 11 or theshoulder member 12.

The quantity of deformation of the lining support section 55 is thedegree of deformation generated by bringing the rotating tool 51 intocontact with the object to be welded 60 and press-fitting the rotatingtool 51 into the object to be welded 60 to push the front surface 60 cof the object to be welded 60. When deformation occurs in the liningsupport section 55, the relative position of the support surface 56 a ofthe lining member 56 changes according to the quantity of deformation.The front surface 60 c of the object to be welded 60, which is supportedby the support surface 56 a, is also displaced, affecting control of thepress-fit depth of the pin member 11 and the shoulder member 12.

The quantity of distortion of the tool fixing section 52 and the tooldriving section 53 is degree of distortion of members, parts, ormechanisms that constitute the tool fixing section 52 and the tooldriving section 53, and is generated by reaction against a force ofpressing the front surface 60 c of the object to be welded 60 when therotating tool 51 contacts and is press-fitted into the object to bewelded 60. When distortion occurs in the tool fixing section 52 and thetool driving section 53, the position of the front ends of the pinmember 11 and the shoulder member 12 changes according to the quantityof distortion, affecting control of the press-fit depth of the pinmember 11 and the shoulder member 12.

The displacement calculating section 24 calculates the quantity ofdisplacement on the basis of the welding condition inputted from theinput section 32, positional information on the rotating tool 51, whichis inputted from the pin driving section 531 and the shoulder drivingsection 532, etc., and the deformation/distortion database Db4 stored inthe memory section 31, etc. The tool driving control section 21 correctsthe tool distance on the basis of the quantity of displacementcalculated by the displacement calculating section 24 and then, controlsthe tool driving section 53. The press-fit depth of the rotating tool 51(the pin member 11, the shoulder member 12, or the both) with respect tothe object to be welded 60 can be preferably controlled.

The configuration of the tool position acquiring section 23 and thedisplacement calculating section 24 is not specifically limited, and inthis embodiment, as long as the tool driving control section 21 isformed of the CPU in the microcomputer as described above, the toolposition acquiring section 23 and the displacement calculating section24 may be functions of the tool driving control section 21. That is, theCPU as the tool driving control section 21 operates according to aprogram stored in the memory section 31 or another memory section torealize the tool position acquiring section 23 and the displacementcalculating section 24. Alternatively, the tool position acquiringsection 23 and the displacement calculating section 24 may be configuredas a well-known logical circuit or like including a switching element, asubtractor, or a comparator, etc.

In this embodiment, the tool driving control section 21 may controldriving of the rotating tool 51 by the output from the press-fitreference point setting section 22, the output from the displacementcalculating section 24, and reading data of the pressurizing force/motorcurrent databases Db1 to Db3 in the memory section 31, or as representedby a broken arrow in FIG. 7, by using the pressurizing force sent fromthe pressurizing force detecting section 33.

In the friction stir spot welding device 50B in this embodiment, thepress-fit reference point setting section 22 can set the press-fitreference point to suitably control the press-fit depth of the pinmember 11 and the shoulder member 12. This effect is the same as that inEmbodiment 1. However, even when quantity of displacement such asquantity of displacement of the rotating tool, quantity of deformationof the lining support section 55, quantity of distortion of the toolfixing section 52 and the tool driving section 53, and backlash of thetool driving section 53 is present, the press-fit depth can be suitablycontrolled by correcting the tool distance acquired by the tool positionacquiring section 23 with the quantity of displacement.

By correcting the tool distance with the quantity of displacement of therotating tool, which is one of the displacement, the possibility thatthe rotating tool 51 penetrates the object to be welded 60 (hole) can beprevented or suppressed. As described in Embodiment 1, in the frictionstir spot welding devices 50A and 50B, since the recess generated due topress-fit of the rotating tool 51 can be backfilled and shaped, suchhole can be also backfilled. Nevertheless, it is desirable to avoid thehole as far as possible. When the press-fit reference point is greatlyshifted due to the quantity of displacement of the rotating tool, thehole can occur. In this embodiment, however, the tool driving controlsection 21 can correct the tool distance with the quantity ofdisplacement to prevent or suppress the hole.

Embodiment 3

Configuration of a friction stir spot welding device in accordance withEmbodiment 3 of the present invention will be specifically describedwith reference to FIG. 8. As shown in FIG. 8, a friction stir spotwelding device 50C in this embodiment is the same as the friction stirspot welding device 50A in Embodiment 1 in basic configuration, but isdifferent from the friction stir spot welding device 50A in that a clampposition-rotating tool position detecting section 34 and a clamp-tooldistance calculating section 25 are provided.

The clamp position-rotating tool position detecting section 34 detectsthe position of the front end of the clamp member 54. The clamp-tooldistance calculating section 25 calculates a clamp-tool distance Dc(refer to a block arrow in FIG. 8) that is a distance between theposition of the front end of the clamp member 54, which is detected bythe clamp position-rotating tool position detecting section 34, and thefront end of the pin member 11 or the shoulder member 12. As describedabove, the clamp member 54 is located outside the shoulder member 12,and serves to press the front surface 60 c of the object to be welded60. Accordingly, as long as the clamp member 54 presses the object to bewelded 60, the front end of the clamp member 54 can be deemed to havethe same position as the front surface 60 c of the object to be welded60.

Therefore, the tool driving control section 21 can suitably control thepress-fit depth of the pin member 11 and the shoulder member 12 on thebasis of the press-fit reference point set by the press-fit referencepoint setting section 22, and can correct quantity of displacement suchas quantity of displacement of shoulder and quantity of distortion asdescribed in Embodiment 2, with the clamp-tool distance Dc calculated bythe clamp-tool distance calculating section 25 and then, adjust (set)the press-fit depth of the pin member 11 and the shoulder member 12.Accordingly, the press-fit depth can be suitably controlled.

Configuration of the clamp position-rotating tool position detectingsection 34 is not specifically limited, and may be any well-knownposition sensor capable of detecting the front end of the clamp member54. Configuration of the clamp-tool distance calculating section 25 isnot also specifically limited, and as described in Embodiment 1 or 2,may be a function of the tool driving control section 21, or may beconfigured as a well-known logical circuit or like including such as aswitching element, a subtractor, or a comparator, etc.

It is noted that, in the friction stir spot welding device 50C inaccordance with Embodiment 3, the pressurizing force detecting section33 is not essential constitute, but be used to acquire the pressurizingforce/motor current databases Db1 to Db3 stored in the memory section31, or can be used as redundant information of the press-fit referencepoint setting section 22, increasing convenience in controlling drivingof the rotating tool 51. In the tool driving control section 21, thepressurizing force detecting section 33 may be used for feedback controlfrom the pressurizing force detecting section 33 in place of thepressurizing force/motor current databases Db1 to Db3.

Embodiment 4

Configuration of a friction stir spot welding device in accordance withEmbodiment 4 of the present invention will be specifically describedwith reference to FIG. 9. As shown in FIG. 9, a friction stir spotwelding device 50D in this embodiment is the same as the friction stirspot welding device 50C in Embodiment 3 in basic configuration, but isdifferent from the friction stir spot welding device 50C in that nolining member 56 is provided, and no pressurizing force detectingsection 33 is provided.

When the lining member 56 cannot support the back surface 60 d of theobject to be welded 60, for example, when a part of a three-dimensionalstructure is welded and thus, there is no space for the lining member56, the lining member 56 cannot be used. When the object to be welded 60has a sufficient stiffness, a lining may be unnecessary. Even in thesecases, the present invention can be preferably applied.

In the example shown in FIG. 9, in the friction stir spot welding device50D, in the state where the clamp member 54 contacts the object to bewelded 60, the press-fit reference point setting section 22 sets thepress-fit reference point, and the tool driving control section 21controls advancement and retraction, and the press-fit depth of therotating tool 51 (the pin member 11 and the shoulder member 12). At thistime, even when the pressurizing force detecting section 33 is notprovided, by previously storing the pressurizing force adjusting data inthe memory section 31, the pressurizing force can be adjusted.

The present invention is not limited to the embodiments, and can bevariously modified within the scope of Claims. Embodiments obtained byappropriately combining the technical means disclosed in the differentembodiments and the modified examples also fall within the technicalscope of the present invention.

Many modifications and other embodiments of the present invention willbe apparent to those skilled in the art from the above description.Therefore, the above description should be interpreted to be onlyillustrative, and serves to teach the best mode for carrying out thepresent invention to those skilled in the art. Details of theconfiguration and/or function can be substantially changed withoutdeviating from the spirit of the present invention.

INDUSTRIAL APPLICABILITY

The present invention can suitably control the position of the pinmember and the shoulder member especially in double-acting friction stirspot welding and therefore, can be applied to various fields usingfriction stir spot welding widely and preferably.

DESCRIPTION OF REFERENCE SIGNS

-   -   11: Pin member    -   12: Shoulder member    -   21: Tool driving control section    -   22: Press-fit reference point setting section    -   23: Tool position acquiring section    -   24: Displacement calculating section    -   25: Clamp-tool distance calculating section    -   31: Memory section    -   33: Pressurizing force detecting section    -   34: Clamp position-rotating tool position detecting section    -   50A, 50B, 50C, 50D: Friction stir spot welding device    -   51: Rotating tool    -   53: Tool driving section    -   54: Clamp member    -   55: Lining support section    -   56: Lining member    -   60: Object to be welded

1. A friction stir spot welding device that welds an object to be weldedby partial stirring of a rotating tool, the device comprising: acylindrical pin member as the rotating tool, the pin member configuredto rotate about an axis and be advanceable and retractable in the axialdirection; a tubular shoulder member configured to surround the pinmember, rotate coaxially with the pin member, and be advanceable andretractable in the axial direction; a tool driving section configured tocause each of the pin member and the shoulder member to advance andretract along the axis; a press-fit reference point setting sectionconfigured to set a position where the pin member or the shoulder membercontacts the object to be welded, as a press-fit reference point; and atool driving control section configured to control the action of thetool driving section, wherein the tool driving control section controlsa relative position of the pin member with respect to the shouldermember or a relative position of the shoulder member with respect to thepin member on the basis of the press-fit reference point set by thepress-fit reference point setting section, thereby controlling apress-fit depth of the pin member or the shoulder member press-fittedfrom a surface of the object to be welded.
 2. The friction stir spotwelding device according to claim 1, further comprising: a displacementcalculating section configured to calculate quantity of displacement asdisplacement of a front end of the pin member or the shoulder member,wherein the tool driving control section is configured to correct thepress-fit depth with the quantity of displacement.
 3. The friction stirspot welding device according to claim 1, further comprising: a clampmember located outside the shoulder member, the clamp member beingconfigured to press the object to be welded from the surface; a clampposition-rotating tool position detecting section configured to detectthe position of a front end of the clamp member; and a clamp-tooldistance calculating section configured to calculate a distance betweenthe front end of the clamp member, which is detected by the clampposition-rotating tool position detecting section, and the front end ofthe pin member or the shoulder member, wherein the tool driving controlsection is configured to adjust the press-fit depth on the basis of thedistance calculated by the clamp-tool distance calculating section. 4.The friction stir spot welding device according to claim 1, furthercomprising a memory section, wherein the memory section is configured tostore pressurizing force adjusting data for adjusting pressurizing forceof the rotating tool press-fitted into the object to be welded, and thetool driving control section is configured to read the pressurizingforce adjusting data from the memory section to control the pressurizingforce.
 5. The friction stir spot welding device according to claim 4,wherein the pressurizing force adjusting data as a value of a currentapplied to a motor of the tool driving section is stored in the memorysection, and the tool driving control section is configured to adjustthe current value to control the pressurizing force.
 6. The frictionstir spot welding device according to claim 4, wherein the memorysection individually stores the pressurizing force adjusting data ineach of a press-fit action of press-fitting the pin member into theobject to be welded, a pull-out action of pulling the pin member out ofthe object to be welded, and stopped state of the pin member, and thetool driving control section determines whether the action of the pinmember is the press-fit action, the pull-out action, or the stoppedstate, and reads the pressurizing force adjusting data corresponding tothe determined action from the memory section to control the tooldriving section.
 7. A friction stir spot welding method using acylindrical pin member configured to rotate about an axis and beadvanceable and retractable in the axial direction, and a tubularshoulder member configured to surround the pin member, rotate coaxiallywith the pin member, and be advanceable and retractable in the axialdirection in a state where the pin member and the shoulder member areadvanceable and retractable, to weld an object to be welded having afront surface facing the pin member and the shoulder member by partialstirring, wherein a position where the pin member or the shoulder membercontacts the object to be welded is set as a press-fit reference point,and a relative position of the pin member with respect to the shouldermember or a relative position of the shoulder member with respect to thepin member is controlled on the basis of the press-fit reference point,thereby controlling a press-fit depth of the pin member or the shouldermember press-fitted from a surface of the object to be welded.
 8. Thefriction stir spot welding method according to claim 7, wherein quantityof displacement as displacement of a front end of the pin member or theshoulder member is calculated, and the press-fit depth is corrected withthe quantity of displacement.
 9. The friction stir spot welding methodaccording to claim 7, wherein the surface of the object to be welded ispressed by a clamp member located outside the shoulder member, and adistance between a front end of the clamp member and a front end of thepin member or the shoulder member is calculated, and the press-fit depthis adjusted on the basis of the distance.
 10. The friction stir spotwelding method according to claim 7, wherein pressurizing forceadjusting data for adjusting pressurizing force of the pin memberpress-fitted into the object to be welded is stored in a memory section,and the pressurizing force adjusting data is read from the memorysection to control the pressurizing force.